This invention relates broadly to a method for determining the latent gas content of metal samples and, in particular, to a method for analyzing solidified steel samples to determine their oxygen content.
At various stages during the production of steel it becomes very important to ascertain the oxygen content of the melt in order to determine, for example, the quantity of deoxidizer which must be added at a later stage in the operation. In most cases, the degree of oxidation of the melt is determined by obtaining a sample of the unkilled or semi-killed molten steel, allowing it to solidify, pyrolizing a segment of the solidified sample in a heat extraction furnace, and quantitatively analyzing the effluent gas in an attached gas chromatograph. U.S. Pat. No. 3,820,380 to Miller et al. discusses several analytical methods of this type.
It has been the practice when obtaining such samples to utilize a sampling device including a cavity which contains a killing agent, such as aluminum, zirconium, silicon, or titanium. The killing agent is present in a sufficient quantity to combine with the free oxygen in the molten sample as it fills the cavity so that upon solidification of the sample there will be no substantial loss of oxygen content and no porosity to interfere with the subsequent analysis. Thus, the resulting solidified test ingot contains not only the metallic oxides which may have been originally present in the melt, but also oxidic compounds formed through the reaction of available oxygen and the killing agent. In the ideal situation, such oxides would be completely disassociated upon pyrolysis and the true oxygen content of the sample determined. However, in the past, this ideal has not been realized because of the relatively high melting points of such metallic oxide compounds or because the molecular bonding between the metal and oxygen constituents was strong enough to resist reduction in the absence of a catalyst such as nickel or platinum. Of course, these catalysts could be employed in the procedure but their relatively high costs made their use on a continuing basis economically impractical.
As a result, the prior art procedures frequently produced unreliable analytical data, particularly in relation to the oxygen content of test samples.